1. Field of the Invention
The invention relates to a liquated gas lighter with non-adjustable flame height, of the type comprising a liquated gas reservoir, a burner provided with a chimney through which a gas flow from said reservoir is sent outside and a gas flow rate limiting device consisting of a microporous membrane gripped between a first seating body and a second seating body, with said first and second seating bodies delimiting a passage area in said membrane.
2. Description of Related Art
With the lighters in the field of the invention, the flame height control is set at a pre-established value by means of a microporous membrane that the gas passes through on its way between the reservoir and the burner. This microporous membrane is gripped between two seating bodies that between them define a passage area in which the membrane faces, on its upstream face, the liquated gas coming from the reservoir and, on its downstream face, a supply duct for supplying gas to the burner. The liquated gas from the reservoir reaches the membrane on said upstream face, diffuses into the microporous material of the membrane and leaves it via said downstream face towards said supply duct. The flow rate of the gas released through the membrane largely depends on the membrane surface that is facing the supply duct for supplying gas to the burner. The surface and the physical characteristics of the membrane thus determine a substantially constant gas outlet flow rate (under normal operating conditions).
This type of lighter must be designed to prevent any possible breakage of the microporous membrane, which, as it is very thin, is not very resistant to mechanical stress. Moreover, in order to ensure a substantially constant gas flow rate, the lighter design must guarantee that there are no variations in the position of the membrane over time. Also, the design must prevent the membrane from experiencing any vibrations. In the lighters of the type under consideration, these difficulties are overcome by gripping the membrane between two seating surfaces, which allows to firmly hold the membrane and exposes only a reduced part of its surface to the direct action of the liquated gas. Even so, the membrane is exposed to breakage by liquated gas from the reservoir arriving suddenly in liquid phase (hereinafter “dynamic surge”). This situation occurs particularly when the lighter is knocked violently. In the known lighters of the type under consideration, this problem is overcome by providing a labyrinth path for the liquated gas route between the reservoir and the membrane. Another known solution consists in arranging some kind of reinforcement over the membrane, such as for example a mesh applied to it.
Also a dangerous increase in the flame height could occur once the lighter has adopted a horizontal position, in which the membrane is permanently wetted by gas in liquid state which ends up accumulating downstream of the membrane. In these circumstances, the gas outlet flow rate can be considerably greater during a short transitory period, until the gas in liquid state, near the membrane, has evaporated. It is important that the design of this type of lighters maintains this transitory situation within acceptable limits.
The known lighters of the type under consideration resolve these problems with greater or lesser success, but they are still not completely satisfactory. In fact, the known lighters require an expensive manufacturing process or, when manufacturing is more economical, the lighters are not as robust.
Spanish patent ES2000690 in the name of the actual applicant discloses a lighter with non-adjustable flame height wherein the first seating body, located upstream from the membrane, has an elongated cylindrical shape and has a longitudinal, peripheral groove for the passage of the liquated gas from the reservoir. This groove comes out into an annular pool formed in said first seating body. The second seating body, downstream from the membrane, has a short straight gas outlet hole that faces said annular pool and leads directly to the stopper system of the burner. Said Spanish patent also discloses a second embodiment of the lighter wherein the passage groove for the liquated gas is in a centred position and comes out into the pool not directly but rather passing via a transverse channel. These designs manage to minimize the dynamic surge on the membrane, thanks to the high pressure drop caused by the length of the liquated gas passage groove. However, these designs suffer from the drawback that they are complicated and expensive to manufacture. Said patent also discloses a third embodiment that is similar to the second, but wherein the first seating body is much shorter. This design is less robust in terms of the membrane's breaking strength with respect to a dynamic surge and, at any event, it is expensive to manufacture because the second seating body has a complicated geometry. In short, the lighter designs disclosed in document ES2000690 can be improved in terms of manufacturing costs and the robustness of the membrane with respect to a dynamic surge. Moreover the outlet flow rate limitation, when the liquated gas that reaches the membrane is in a liquid phase, can be improved.
Documents EP0047708 and U.S. Pat. No. 4,224,020 disclose liquated gas lighters with a non-adjustable flame height that are shaped generally like the lighters under consideration, but with the important difference that between the membrane and the second seating body a porous layer is arranged as a reinforcement that prevents the membrane from breaking as a result of a dynamic pressure surge. This porous reinforcement layer allows the membrane to be exposed more directly to the gas ducts defined in the seating bodies, which can then be straight, directly facing each other and with a larger diameter. This solution has the advantage that the seating bodies have a simple geometry. However, it is important to bear in mind that this simple geometry is not viable without the said porous reinforcement layer, which, in fact, considerably increases the manufacturing cost of the lighter.